It is a great list. However, almost all (if not all) of the authors have shuffled off this mortal coil. That does not mean their stories should also shuffle off to Buffalo. However, I wonder if we could not add to this list by looking at story collections from Michael Cart, Jane Yolen, Donald Gallo and others? Here are a dozen titles. Each collection has more than a handful of stories, all written by contemporary YA authors.
This is by no means complete. However, this should prove to be an excellent resource that exptends the short story well beyond the textbooks and anthologies.